Check weighing apparatus for articles

ABSTRACT

A check-weighing apparatus is provided wherein a conveyor feeds articles in a discrete manner onto a weighing device, the feeding of the articles being terminated, and the articles being removed from the weighing device, when a predetermined weight is attained. A receptacle receives a batch of articles from the conveyor and when a predetermined batch quantity is attained within the receptacle which is less than the predetermined weight referred to, the batch is released onto the weighing device. The conveyor then tops up the batch to the predetermined weight.

This invention relates to apparatus for check weighing articles andparticularly but not exclusively to the check-weighing of foodstuffssuch as potato crisps or similar low density snack food.

In known crisp check weighing and packing machines the crisps areconveyed by vibrating conveyors to a packing station. The crisps falldiscretely from the end of the last conveyor into a downwardly slopingpan. The pan has a gate at its lowermost end behind which crisps areallowed to accumulate. The pan is mounted on weighing scales whichindicate the weight of crisps accumulating behind the gate. When thescales indicate that a predetermined weight of crisps has accumulated,the vibrating conveyors halt, the gate opens and allows the crisps tofall into a waiting bag.

There are several problems associated with this check weighingprocedure. Because crisps are light and irregularly shaped, it isdifficult to supply a regular weight and quantity of crisps to the scalepan and thence to each bag. Additionally, since the only convenientmethod of introducing crisps into bags is by gravity feed, the momentumof the crisps falling into the pan causes the scales to read high thustending to produce an unacceptably high percentage of bags of crispswhose contents are underweight. In order to minimize the number ofunderweight filled bags the rate of feed along the vibrating conveyorshas to be increased. This increase in feed rate does reduce the numberof underweight bags but also increases unacceptably the number of bagsthat are overweight.

It is an object of the present invention to provide an apparatus whichimproves the crisp feed to a packing machine, in particular to provide acommercially acceptable constant weight of crisps per bag. The apparatusis designed for addition to existing equipment for crisp packing.

According to the present invention there is provided check-weighingapparatus comprising a weighing device, conveyor means to feed articlesdiscretely onto the weighing device, and first control means responsiveon the attainment of a predetermined weight of articles on the weighingdevice to halt the feed of articles from the conveyor means and toremove the articles from the weighing device, characterised in thatthere is provided receptacle means to receive a batch of articles fromthe conveyor means, and second control means responsive on theattainment of a predetermined batch quantity within the receptaclemeans, being less than said predetermined weight of articles, to releasesaid batch of articles to the weighing device and thereafter to permitthe conveyor means to top up said batch on the weighing device to saidpredetermined weight.

By way of example the invention will now be described with reference tothe accompanying diagrammatic drawings in which,

FIG. 1 is a side elevation of a check weighing apparatus,

FIG. 2 is an enlarged detail portion of the apparatus of FIG. 1, and

FIG. 3 shows in block form a control unit for the apparatus of FIGS. 1and 2.

Referring to FIGS. 1 and 2 a conveyor means comprising a first vibratoryconveyor 10 is positioned above and partly overlapping a secondvibratory conveyor 11. Conveyor 10 is arranged to supply conveyor 11with potato crisps. Both conveyors are actuated by known vibrating means(not shown).

The second conveyor 11 is provided at its downstream end with areceptacle means comprising an integral chute 12 having in its lower (ordownstream) portion a gate 13 arranged to be opened and shut by asolenoid 16 through a lever linkage 21, 22, 23, 24. Linkage and gate 13are supported by a plate 20 depending from the solenoid 16.

When gate 13 is closed, chute 12 and gate 13 together form a pocket,otherwise receptacle, in which crisps falling off the conveyor 11 areallowed to accumulate.

When gate 13 is open, chute 12 is arranged to discharge crisps into aweighing device comprising a sloping pan 14 mounted on weighing scales15. Chute 12 and pan 14 are parallel, that is, have a commoninclination, thus minimizing the momentum of the crisps as they fallinto the pan 14 for weighing. Pan 14 is provided at its bottom end witha gate 19 which is arranged to open when the scales 15 indicate that apredetermined weight of crisps has collected in the pan 14, and to beclosed when there are no crisps in the pan.

Referring to FIG. 3, a first control means or known normal feed relay(not illustrated, but indicated by "n.f.r.") is in series with a secondcontrol means provided by a timer T and relay R in series. The timer Tis activated by the normal feed relay which operates a crisp packingmachine in known fashion. The relay R is in turn energised by the timerfor whatever length of time the timer has been set.

The relay is in series with a pair of control units C1 and C2 whichcontrol the vibrator machinery (not illustrated) for the conveyors 10and 11 respectively. When the relay is energised by the timer an impulsepasses to each of the control units which consequently control theconveyors. The vibratory conveyors may therefore be controlled either bytheir conventional circuitry (n.f.r.) or by the timer via the relay.

The weighing scales is provided with signal generating devices toindicate (a) the presence of a predetermined weight of crisps in the pan14, and (b) the absence of any crisps in the pan.

On receiving a signal from the weighing scales indicating that thepredetermined weight has been attained, the normal feed relay opens gate19, thus releasing the crisps from the pan 14 into a packaging bag (notshown) and switches off the vibratory conveyors to prevent an overloadof crisps from entering the bag. When the pan is empty, the normal feedrelay received signal (b) from the weighing scales, closes gate 19 andactivates the second control means (the timer and relay).

On receiving the activating signal, the second control means closes gate13 by means of solenoid 16 and restarts the vibratory conveyors, thusconveying crisps into the receptacle provided by chute 12 and gate 13.The size of the batch of crisps entering the chute is determined by thesetting of the timer and is conveniently between 1/2 to 2/3 of thepredetermined weight of the crisps entering the bag from the pan. Whenthe desired quantity of crisps in the batch has been attained, the timeractivates the relay to open gate 13 and release the batch into the emptypan 14. The gate 13 is then held open whilst further crisps from theconveyors follow the batch down the chute into the pan until the batchis topped up to the predetermined weight for a bag of crisps. When thisoccurs signal (a) is again generated and the cycle recommences.

The timing may be arranged that in practice it is convenient for gate 13to shut practically simultaneously with the opening of gate 19, so thatthe vibratory movement of the conveyors ceases for only a very shortperiod in the cycle.

It is convenient to provide a skirt 17 attached to the bottom surface ofthe chute 12 near its downstream end to prevent crisps from beingknocked out of the chute 12 by the closing movement of the gate 13. Itis likewise convenient to provide a flange 18 depending from thelowermost portion of gate 13 and overlapping the end of the chute 12 inorder to close the chute more effectively.

It is found with the apparatus of the invention that a commerciallyacceptable constant weight of crisps in bags may be obtained.

The apparatus of the invention may be applied to batch-wise weighing andpackaging of discrete products such as light density snack foods andparticulate materials.

Modifications may be made within the scope of the invention. Forexample, the first control means (n.f.r.) may be arranged to close gate13 simultaneously with the opening of gate 19 rather than first activatethe second control means. It will be understood that "gate" includesclosure members such as shutters, diaphragm, and butterfly valves, whichmay be useful in some circumstances.

Types of conveyor other than vibratory may be contemplated, such as beltconveyors. The control means may be electronic or fluidic circuits, ormay be purely mechanical in nature. The control means may be arranged tocontrol the speed of the conveyors rather than switching them on andoff. Although two conveyors are described there may of course be more oreven one. The chute 12 in some applications need not necessarily beintegral with the conveyor means.

Other kinds of weighing devices such as strain gauges may be used insome applications.

What I claim is:
 1. Check-weighing apparatus comprising,(a) a conveyor,(b) receptacle means for receiving articles from said conveyor, (c) afirst gate in the receptacle means for providing an exit for articlesfrom said receptacle means, (d) a weighing device comprising a weighingpan and means responsive to the weight in said weighing pan, theweighing pan being located beneath the exit from the receptacle means toreceive articles therefrom, (e) means for releasing articles from theweighing pan, (f) first control means, responsive to the attainment of apredetermined weight of articles on the weighing pan, for releasing thepredetermined weight of articles from the weighing pan and for haltingthe feed of articles to the receptacle means from the conveyor, (g)second control means for controlling the feed of articles from theconveyor into the receptacle means until a required quantity of articlesis attained which is less than the predetermined weight of articles tobe weighed by the weighing device, for, responsive to said requiredquantity being attained, opening the first gate and releasing therequired quantity of articles into the weighing pan and for thereafterpermitting the conveyor to feed through the receptacle means to top upthe articles on the weighing pan to the predetermined weight. 2.Apparatus as claimed in claim 1 wherein the control means compriseelectromechanical circuits.
 3. Apparatus as claimed in claim 1 whereinthe second control means includes a timer for regulating feed ofarticles from the conveyor means.
 4. Apparatus as claimed in claim 1wherein the receptacle means comprises a chute and the weighing pancomprises a pan downwardly sloping therefrom, the chute and pan beingsubstantially parallel.
 5. Apparatus as claimed in claim 1 wherein theconveyor means comprises a vibrating conveyor.
 6. Apparatus as claimedin claim 1 wherein the conveyor means comprises first and secondvibratory conveyors, the second conveyor being below the level of andpartly overlapping by the first conveyor.
 7. Apparatus as claimed inclaim 1 wherein the second control means includes a solenoid arranged toopen and close the first gate by a lever linkage.
 8. Apparatus asclaimed in claim 1 wherein the receptacle means comprises a chute andthe first gate is provided in a lower portion of said chute. 9.Apparatus as claimed in claim 8 wherein the chute is integral with theconveyor means.
 10. Apparatus as claimed in claim 1 wherein the weighingpan is a pan downwardly sloping from the receptacle means.
 11. Apparatusas claimed in claim 10 wherein the means for releasing articles from theweighing pan comprises a second gate in the weighing pan, the secondgate being controlled by the first control means.
 12. Apparatus asclaimed in claim 11 wherein the first control means is arranged, onreceipt of a signal from the means responsive to the weight in theweighing pan signifying zero weight on the pan, to close the second gateand activate the second control means.
 13. Apparatus as claimed in claim12 wherein the second control means is arranged, on activation, to closethe first gate and to control the feed of articles from the conveyormeans until the required quantity of articles is attained in thereceptacle means, whereupon the second control means opens the firstgate.